Leadframe Strip Testing With Extended Contact Area
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Solution Overview
Problem
Conventional leadframe strip testing methods are limited by the small contact area available for probing leads, particularly in high-current packages, due to the need to sever leads along a final lead outline, which restricts the ability to test packages rated for high currents effectively.
Innovation Solution
The method involves electrically isolating leads from the periphery of the leadframe strip such that they extend beyond the final lead outline, providing additional contact area for probing during testing, and then severing the unit leadframes along the final lead outline after testing, allowing for improved ease and higher current testing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If leads are severed along the final lead outline for electrical isolation, then electrical isolation is achieved, but the contact area for probing leads is reduced
Solution Approach 1:
The patent segments the leadframe strip into multiple unit leadframes with staggered lead orientations. By alternating the orientation of leads in adjacent unit leadframes, the invention creates multiple probing paths, allowing test probes to access leads through different locations and angles, thereby compensating for the reduced contact area in any single location.
Solution Approach 2:
The patent utilizes the dimensional arrangement of leads extending in alternating directions (e.g., leftward and rightward orientations) to create multiple spatial access points for probing. This dimensional diversification allows testing to proceed despite limited contact area at any given location, as probes can approach from different directions.
2Reliability
If leads are severed early for electrical isolation, then electrical isolation is achieved, but testing capability for high current packages is compromised
Solution Approach 1:
The patent divides the leadframe strip into multiple unit leadframes that can be tested independently or in groups. This segmentation allows flexible testing configurations where high current packages can be tested with appropriate current distribution across multiple units, while maintaining electrical isolation between units through the severed leads.
Solution Approach 2:
The patent creates a universal testing approach where the same leadframe strip structure can accommodate both high current and low current package testing. The alternating lead orientations and electrical isolation design allow the system to adapt to different current ratings and testing requirements, making the testing apparatus versatile across different package types.
Data Source
AI summary
A leadframe strip includes a plurality of unit leadframes connected to a periphery of the leadframe strip, each unit leadframe having a die paddle, a plurality of leads and a semiconductor die attached to the die paddle. The leadframe strip is tested by electrically isolating at least the leads from the periphery of the leadframe strip such that at least some of the leads extend uninterrupted beyond a final lead outline of the unit leadframes after electrical isolation from the periphery of the leadframe strip. The semiconductor dies are tested, which includes probing the die paddles and the leads that extend uninterrupted beyond the final lead outline of the unit leadframes after electrical isolation from the periphery of the leadframe strip. The unit leadframes are severed from the leadframe strip along the final lead outline of the unit leadframes after testing the semiconductor dies.